core/fmt/builders.rs
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#![allow(unused_imports)]
use crate::fmt::{self, Debug, Formatter};
struct PadAdapter<'buf, 'state> {
buf: &'buf mut (dyn fmt::Write + 'buf),
state: &'state mut PadAdapterState,
}
struct PadAdapterState {
on_newline: bool,
}
impl Default for PadAdapterState {
fn default() -> Self {
PadAdapterState { on_newline: true }
}
}
impl<'buf, 'state> PadAdapter<'buf, 'state> {
fn wrap<'slot, 'fmt: 'buf + 'slot>(
fmt: &'fmt mut fmt::Formatter<'_>,
slot: &'slot mut Option<Self>,
state: &'state mut PadAdapterState,
) -> fmt::Formatter<'slot> {
fmt.wrap_buf(move |buf| slot.insert(PadAdapter { buf, state }))
}
}
impl fmt::Write for PadAdapter<'_, '_> {
fn write_str(&mut self, s: &str) -> fmt::Result {
for s in s.split_inclusive('\n') {
if self.state.on_newline {
self.buf.write_str(" ")?;
}
self.state.on_newline = s.ends_with('\n');
self.buf.write_str(s)?;
}
Ok(())
}
fn write_char(&mut self, c: char) -> fmt::Result {
if self.state.on_newline {
self.buf.write_str(" ")?;
}
self.state.on_newline = c == '\n';
self.buf.write_char(c)
}
}
/// A struct to help with [`fmt::Debug`](Debug) implementations.
///
/// This is useful when you wish to output a formatted struct as a part of your
/// [`Debug::fmt`] implementation.
///
/// This can be constructed by the [`Formatter::debug_struct`] method.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo {
/// bar: i32,
/// baz: String,
/// }
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_struct("Foo")
/// .field("bar", &self.bar)
/// .field("baz", &self.baz)
/// .finish()
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo { bar: 10, baz: "Hello World".to_string() }),
/// r#"Foo { bar: 10, baz: "Hello World" }"#,
/// );
/// ```
#[must_use = "must eventually call `finish()` on Debug builders"]
#[allow(missing_debug_implementations)]
#[stable(feature = "debug_builders", since = "1.2.0")]
#[rustc_diagnostic_item = "DebugStruct"]
pub struct DebugStruct<'a, 'b: 'a> {
fmt: &'a mut fmt::Formatter<'b>,
result: fmt::Result,
has_fields: bool,
}
pub(super) fn debug_struct_new<'a, 'b>(
fmt: &'a mut fmt::Formatter<'b>,
name: &str,
) -> DebugStruct<'a, 'b> {
let result = fmt.write_str(name);
DebugStruct { fmt, result, has_fields: false }
}
impl<'a, 'b: 'a> DebugStruct<'a, 'b> {
/// Adds a new field to the generated struct output.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Bar {
/// bar: i32,
/// another: String,
/// }
///
/// impl fmt::Debug for Bar {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_struct("Bar")
/// .field("bar", &self.bar) // We add `bar` field.
/// .field("another", &self.another) // We add `another` field.
/// // We even add a field which doesn't exist (because why not?).
/// .field("nonexistent_field", &1)
/// .finish() // We're good to go!
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Bar { bar: 10, another: "Hello World".to_string() }),
/// r#"Bar { bar: 10, another: "Hello World", nonexistent_field: 1 }"#,
/// );
/// ```
#[stable(feature = "debug_builders", since = "1.2.0")]
pub fn field(&mut self, name: &str, value: &dyn fmt::Debug) -> &mut Self {
self.field_with(name, |f| value.fmt(f))
}
/// Adds a new field to the generated struct output.
///
/// This method is equivalent to [`DebugStruct::field`], but formats the
/// value using a provided closure rather than by calling [`Debug::fmt`].
#[unstable(feature = "debug_closure_helpers", issue = "117729")]
pub fn field_with<F>(&mut self, name: &str, value_fmt: F) -> &mut Self
where
F: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
{
self.result = self.result.and_then(|_| {
if self.is_pretty() {
if !self.has_fields {
self.fmt.write_str(" {\n")?;
}
let mut slot = None;
let mut state = Default::default();
let mut writer = PadAdapter::wrap(self.fmt, &mut slot, &mut state);
writer.write_str(name)?;
writer.write_str(": ")?;
value_fmt(&mut writer)?;
writer.write_str(",\n")
} else {
let prefix = if self.has_fields { ", " } else { " { " };
self.fmt.write_str(prefix)?;
self.fmt.write_str(name)?;
self.fmt.write_str(": ")?;
value_fmt(self.fmt)
}
});
self.has_fields = true;
self
}
/// Marks the struct as non-exhaustive, indicating to the reader that there are some other
/// fields that are not shown in the debug representation.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Bar {
/// bar: i32,
/// hidden: f32,
/// }
///
/// impl fmt::Debug for Bar {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_struct("Bar")
/// .field("bar", &self.bar)
/// .finish_non_exhaustive() // Show that some other field(s) exist.
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Bar { bar: 10, hidden: 1.0 }),
/// "Bar { bar: 10, .. }",
/// );
/// ```
#[stable(feature = "debug_non_exhaustive", since = "1.53.0")]
pub fn finish_non_exhaustive(&mut self) -> fmt::Result {
self.result = self.result.and_then(|_| {
if self.has_fields {
if self.is_pretty() {
let mut slot = None;
let mut state = Default::default();
let mut writer = PadAdapter::wrap(self.fmt, &mut slot, &mut state);
writer.write_str("..\n")?;
self.fmt.write_str("}")
} else {
self.fmt.write_str(", .. }")
}
} else {
self.fmt.write_str(" { .. }")
}
});
self.result
}
/// Finishes output and returns any error encountered.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Bar {
/// bar: i32,
/// baz: String,
/// }
///
/// impl fmt::Debug for Bar {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_struct("Bar")
/// .field("bar", &self.bar)
/// .field("baz", &self.baz)
/// .finish() // You need to call it to "finish" the
/// // struct formatting.
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Bar { bar: 10, baz: "Hello World".to_string() }),
/// r#"Bar { bar: 10, baz: "Hello World" }"#,
/// );
/// ```
#[stable(feature = "debug_builders", since = "1.2.0")]
pub fn finish(&mut self) -> fmt::Result {
if self.has_fields {
self.result = self.result.and_then(|_| {
if self.is_pretty() { self.fmt.write_str("}") } else { self.fmt.write_str(" }") }
});
}
self.result
}
fn is_pretty(&self) -> bool {
self.fmt.alternate()
}
}
/// A struct to help with [`fmt::Debug`](Debug) implementations.
///
/// This is useful when you wish to output a formatted tuple as a part of your
/// [`Debug::fmt`] implementation.
///
/// This can be constructed by the [`Formatter::debug_tuple`] method.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(i32, String);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_tuple("Foo")
/// .field(&self.0)
/// .field(&self.1)
/// .finish()
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(10, "Hello World".to_string())),
/// r#"Foo(10, "Hello World")"#,
/// );
/// ```
#[must_use = "must eventually call `finish()` on Debug builders"]
#[allow(missing_debug_implementations)]
#[stable(feature = "debug_builders", since = "1.2.0")]
pub struct DebugTuple<'a, 'b: 'a> {
fmt: &'a mut fmt::Formatter<'b>,
result: fmt::Result,
fields: usize,
empty_name: bool,
}
pub(super) fn debug_tuple_new<'a, 'b>(
fmt: &'a mut fmt::Formatter<'b>,
name: &str,
) -> DebugTuple<'a, 'b> {
let result = fmt.write_str(name);
DebugTuple { fmt, result, fields: 0, empty_name: name.is_empty() }
}
impl<'a, 'b: 'a> DebugTuple<'a, 'b> {
/// Adds a new field to the generated tuple struct output.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(i32, String);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_tuple("Foo")
/// .field(&self.0) // We add the first field.
/// .field(&self.1) // We add the second field.
/// .finish() // We're good to go!
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(10, "Hello World".to_string())),
/// r#"Foo(10, "Hello World")"#,
/// );
/// ```
#[stable(feature = "debug_builders", since = "1.2.0")]
pub fn field(&mut self, value: &dyn fmt::Debug) -> &mut Self {
self.field_with(|f| value.fmt(f))
}
/// Adds a new field to the generated tuple struct output.
///
/// This method is equivalent to [`DebugTuple::field`], but formats the
/// value using a provided closure rather than by calling [`Debug::fmt`].
#[unstable(feature = "debug_closure_helpers", issue = "117729")]
pub fn field_with<F>(&mut self, value_fmt: F) -> &mut Self
where
F: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
{
self.result = self.result.and_then(|_| {
if self.is_pretty() {
if self.fields == 0 {
self.fmt.write_str("(\n")?;
}
let mut slot = None;
let mut state = Default::default();
let mut writer = PadAdapter::wrap(self.fmt, &mut slot, &mut state);
value_fmt(&mut writer)?;
writer.write_str(",\n")
} else {
let prefix = if self.fields == 0 { "(" } else { ", " };
self.fmt.write_str(prefix)?;
value_fmt(self.fmt)
}
});
self.fields += 1;
self
}
/// Marks the tuple struct as non-exhaustive, indicating to the reader that there are some
/// other fields that are not shown in the debug representation.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(i32, String);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_tuple("Foo")
/// .field(&self.0)
/// .finish_non_exhaustive() // Show that some other field(s) exist.
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(10, "secret!".to_owned())),
/// "Foo(10, ..)",
/// );
/// ```
#[stable(feature = "debug_more_non_exhaustive", since = "1.83.0")]
pub fn finish_non_exhaustive(&mut self) -> fmt::Result {
self.result = self.result.and_then(|_| {
if self.fields > 0 {
if self.is_pretty() {
let mut slot = None;
let mut state = Default::default();
let mut writer = PadAdapter::wrap(self.fmt, &mut slot, &mut state);
writer.write_str("..\n")?;
self.fmt.write_str(")")
} else {
self.fmt.write_str(", ..)")
}
} else {
self.fmt.write_str("(..)")
}
});
self.result
}
/// Finishes output and returns any error encountered.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(i32, String);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_tuple("Foo")
/// .field(&self.0)
/// .field(&self.1)
/// .finish() // You need to call it to "finish" the
/// // tuple formatting.
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(10, "Hello World".to_string())),
/// r#"Foo(10, "Hello World")"#,
/// );
/// ```
#[stable(feature = "debug_builders", since = "1.2.0")]
pub fn finish(&mut self) -> fmt::Result {
if self.fields > 0 {
self.result = self.result.and_then(|_| {
if self.fields == 1 && self.empty_name && !self.is_pretty() {
self.fmt.write_str(",")?;
}
self.fmt.write_str(")")
});
}
self.result
}
fn is_pretty(&self) -> bool {
self.fmt.alternate()
}
}
/// A helper used to print list-like items with no special formatting.
struct DebugInner<'a, 'b: 'a> {
fmt: &'a mut fmt::Formatter<'b>,
result: fmt::Result,
has_fields: bool,
}
impl<'a, 'b: 'a> DebugInner<'a, 'b> {
fn entry_with<F>(&mut self, entry_fmt: F)
where
F: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
{
self.result = self.result.and_then(|_| {
if self.is_pretty() {
if !self.has_fields {
self.fmt.write_str("\n")?;
}
let mut slot = None;
let mut state = Default::default();
let mut writer = PadAdapter::wrap(self.fmt, &mut slot, &mut state);
entry_fmt(&mut writer)?;
writer.write_str(",\n")
} else {
if self.has_fields {
self.fmt.write_str(", ")?
}
entry_fmt(self.fmt)
}
});
self.has_fields = true;
}
fn is_pretty(&self) -> bool {
self.fmt.alternate()
}
}
/// A struct to help with [`fmt::Debug`](Debug) implementations.
///
/// This is useful when you wish to output a formatted set of items as a part
/// of your [`Debug::fmt`] implementation.
///
/// This can be constructed by the [`Formatter::debug_set`] method.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<i32>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_set().entries(self.0.iter()).finish()
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![10, 11])),
/// "{10, 11}",
/// );
/// ```
#[must_use = "must eventually call `finish()` on Debug builders"]
#[allow(missing_debug_implementations)]
#[stable(feature = "debug_builders", since = "1.2.0")]
pub struct DebugSet<'a, 'b: 'a> {
inner: DebugInner<'a, 'b>,
}
pub(super) fn debug_set_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugSet<'a, 'b> {
let result = fmt.write_str("{");
DebugSet { inner: DebugInner { fmt, result, has_fields: false } }
}
impl<'a, 'b: 'a> DebugSet<'a, 'b> {
/// Adds a new entry to the set output.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<i32>, Vec<u32>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_set()
/// .entry(&self.0) // Adds the first "entry".
/// .entry(&self.1) // Adds the second "entry".
/// .finish()
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![10, 11], vec![12, 13])),
/// "{[10, 11], [12, 13]}",
/// );
/// ```
#[stable(feature = "debug_builders", since = "1.2.0")]
pub fn entry(&mut self, entry: &dyn fmt::Debug) -> &mut Self {
self.inner.entry_with(|f| entry.fmt(f));
self
}
/// Adds a new entry to the set output.
///
/// This method is equivalent to [`DebugSet::entry`], but formats the
/// entry using a provided closure rather than by calling [`Debug::fmt`].
#[unstable(feature = "debug_closure_helpers", issue = "117729")]
pub fn entry_with<F>(&mut self, entry_fmt: F) -> &mut Self
where
F: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
{
self.inner.entry_with(entry_fmt);
self
}
/// Adds the contents of an iterator of entries to the set output.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<i32>, Vec<u32>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_set()
/// .entries(self.0.iter()) // Adds the first "entry".
/// .entries(self.1.iter()) // Adds the second "entry".
/// .finish()
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![10, 11], vec![12, 13])),
/// "{10, 11, 12, 13}",
/// );
/// ```
#[stable(feature = "debug_builders", since = "1.2.0")]
pub fn entries<D, I>(&mut self, entries: I) -> &mut Self
where
D: fmt::Debug,
I: IntoIterator<Item = D>,
{
for entry in entries {
self.entry(&entry);
}
self
}
/// Marks the set as non-exhaustive, indicating to the reader that there are some other
/// elements that are not shown in the debug representation.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<i32>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// // Print at most two elements, abbreviate the rest
/// let mut f = fmt.debug_set();
/// let mut f = f.entries(self.0.iter().take(2));
/// if self.0.len() > 2 {
/// f.finish_non_exhaustive()
/// } else {
/// f.finish()
/// }
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![1, 2, 3, 4])),
/// "{1, 2, ..}",
/// );
/// ```
#[stable(feature = "debug_more_non_exhaustive", since = "1.83.0")]
pub fn finish_non_exhaustive(&mut self) -> fmt::Result {
self.inner.result = self.inner.result.and_then(|_| {
if self.inner.has_fields {
if self.inner.is_pretty() {
let mut slot = None;
let mut state = Default::default();
let mut writer = PadAdapter::wrap(self.inner.fmt, &mut slot, &mut state);
writer.write_str("..\n")?;
self.inner.fmt.write_str("}")
} else {
self.inner.fmt.write_str(", ..}")
}
} else {
self.inner.fmt.write_str("..}")
}
});
self.inner.result
}
/// Finishes output and returns any error encountered.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<i32>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_set()
/// .entries(self.0.iter())
/// .finish() // Ends the set formatting.
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![10, 11])),
/// "{10, 11}",
/// );
/// ```
#[stable(feature = "debug_builders", since = "1.2.0")]
pub fn finish(&mut self) -> fmt::Result {
self.inner.result = self.inner.result.and_then(|_| self.inner.fmt.write_str("}"));
self.inner.result
}
}
/// A struct to help with [`fmt::Debug`](Debug) implementations.
///
/// This is useful when you wish to output a formatted list of items as a part
/// of your [`Debug::fmt`] implementation.
///
/// This can be constructed by the [`Formatter::debug_list`] method.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<i32>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_list().entries(self.0.iter()).finish()
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![10, 11])),
/// "[10, 11]",
/// );
/// ```
#[must_use = "must eventually call `finish()` on Debug builders"]
#[allow(missing_debug_implementations)]
#[stable(feature = "debug_builders", since = "1.2.0")]
pub struct DebugList<'a, 'b: 'a> {
inner: DebugInner<'a, 'b>,
}
pub(super) fn debug_list_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugList<'a, 'b> {
let result = fmt.write_str("[");
DebugList { inner: DebugInner { fmt, result, has_fields: false } }
}
impl<'a, 'b: 'a> DebugList<'a, 'b> {
/// Adds a new entry to the list output.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<i32>, Vec<u32>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_list()
/// .entry(&self.0) // We add the first "entry".
/// .entry(&self.1) // We add the second "entry".
/// .finish()
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![10, 11], vec![12, 13])),
/// "[[10, 11], [12, 13]]",
/// );
/// ```
#[stable(feature = "debug_builders", since = "1.2.0")]
pub fn entry(&mut self, entry: &dyn fmt::Debug) -> &mut Self {
self.inner.entry_with(|f| entry.fmt(f));
self
}
/// Adds a new entry to the list output.
///
/// This method is equivalent to [`DebugList::entry`], but formats the
/// entry using a provided closure rather than by calling [`Debug::fmt`].
#[unstable(feature = "debug_closure_helpers", issue = "117729")]
pub fn entry_with<F>(&mut self, entry_fmt: F) -> &mut Self
where
F: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
{
self.inner.entry_with(entry_fmt);
self
}
/// Adds the contents of an iterator of entries to the list output.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<i32>, Vec<u32>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_list()
/// .entries(self.0.iter())
/// .entries(self.1.iter())
/// .finish()
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![10, 11], vec![12, 13])),
/// "[10, 11, 12, 13]",
/// );
/// ```
#[stable(feature = "debug_builders", since = "1.2.0")]
pub fn entries<D, I>(&mut self, entries: I) -> &mut Self
where
D: fmt::Debug,
I: IntoIterator<Item = D>,
{
for entry in entries {
self.entry(&entry);
}
self
}
/// Marks the list as non-exhaustive, indicating to the reader that there are some other
/// elements that are not shown in the debug representation.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<i32>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// // Print at most two elements, abbreviate the rest
/// let mut f = fmt.debug_list();
/// let mut f = f.entries(self.0.iter().take(2));
/// if self.0.len() > 2 {
/// f.finish_non_exhaustive()
/// } else {
/// f.finish()
/// }
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![1, 2, 3, 4])),
/// "[1, 2, ..]",
/// );
/// ```
#[stable(feature = "debug_more_non_exhaustive", since = "1.83.0")]
pub fn finish_non_exhaustive(&mut self) -> fmt::Result {
self.inner.result.and_then(|_| {
if self.inner.has_fields {
if self.inner.is_pretty() {
let mut slot = None;
let mut state = Default::default();
let mut writer = PadAdapter::wrap(self.inner.fmt, &mut slot, &mut state);
writer.write_str("..\n")?;
self.inner.fmt.write_str("]")
} else {
self.inner.fmt.write_str(", ..]")
}
} else {
self.inner.fmt.write_str("..]")
}
})
}
/// Finishes output and returns any error encountered.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<i32>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_list()
/// .entries(self.0.iter())
/// .finish() // Ends the list formatting.
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![10, 11])),
/// "[10, 11]",
/// );
/// ```
#[stable(feature = "debug_builders", since = "1.2.0")]
pub fn finish(&mut self) -> fmt::Result {
self.inner.result = self.inner.result.and_then(|_| self.inner.fmt.write_str("]"));
self.inner.result
}
}
/// A struct to help with [`fmt::Debug`](Debug) implementations.
///
/// This is useful when you wish to output a formatted map as a part of your
/// [`Debug::fmt`] implementation.
///
/// This can be constructed by the [`Formatter::debug_map`] method.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<(String, i32)>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_map().entries(self.0.iter().map(|&(ref k, ref v)| (k, v))).finish()
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
/// r#"{"A": 10, "B": 11}"#,
/// );
/// ```
#[must_use = "must eventually call `finish()` on Debug builders"]
#[allow(missing_debug_implementations)]
#[stable(feature = "debug_builders", since = "1.2.0")]
pub struct DebugMap<'a, 'b: 'a> {
fmt: &'a mut fmt::Formatter<'b>,
result: fmt::Result,
has_fields: bool,
has_key: bool,
// The state of newlines is tracked between keys and values
state: PadAdapterState,
}
pub(super) fn debug_map_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>) -> DebugMap<'a, 'b> {
let result = fmt.write_str("{");
DebugMap { fmt, result, has_fields: false, has_key: false, state: Default::default() }
}
impl<'a, 'b: 'a> DebugMap<'a, 'b> {
/// Adds a new entry to the map output.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<(String, i32)>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_map()
/// .entry(&"whole", &self.0) // We add the "whole" entry.
/// .finish()
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
/// r#"{"whole": [("A", 10), ("B", 11)]}"#,
/// );
/// ```
#[stable(feature = "debug_builders", since = "1.2.0")]
pub fn entry(&mut self, key: &dyn fmt::Debug, value: &dyn fmt::Debug) -> &mut Self {
self.key(key).value(value)
}
/// Adds the key part of a new entry to the map output.
///
/// This method, together with `value`, is an alternative to `entry` that
/// can be used when the complete entry isn't known upfront. Prefer the `entry`
/// method when it's possible to use.
///
/// # Panics
///
/// `key` must be called before `value` and each call to `key` must be followed
/// by a corresponding call to `value`. Otherwise this method will panic.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<(String, i32)>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_map()
/// .key(&"whole").value(&self.0) // We add the "whole" entry.
/// .finish()
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
/// r#"{"whole": [("A", 10), ("B", 11)]}"#,
/// );
/// ```
#[stable(feature = "debug_map_key_value", since = "1.42.0")]
pub fn key(&mut self, key: &dyn fmt::Debug) -> &mut Self {
self.key_with(|f| key.fmt(f))
}
/// Adds the key part of a new entry to the map output.
///
/// This method is equivalent to [`DebugMap::key`], but formats the
/// key using a provided closure rather than by calling [`Debug::fmt`].
#[unstable(feature = "debug_closure_helpers", issue = "117729")]
pub fn key_with<F>(&mut self, key_fmt: F) -> &mut Self
where
F: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
{
self.result = self.result.and_then(|_| {
assert!(
!self.has_key,
"attempted to begin a new map entry \
without completing the previous one"
);
if self.is_pretty() {
if !self.has_fields {
self.fmt.write_str("\n")?;
}
let mut slot = None;
self.state = Default::default();
let mut writer = PadAdapter::wrap(self.fmt, &mut slot, &mut self.state);
key_fmt(&mut writer)?;
writer.write_str(": ")?;
} else {
if self.has_fields {
self.fmt.write_str(", ")?
}
key_fmt(self.fmt)?;
self.fmt.write_str(": ")?;
}
self.has_key = true;
Ok(())
});
self
}
/// Adds the value part of a new entry to the map output.
///
/// This method, together with `key`, is an alternative to `entry` that
/// can be used when the complete entry isn't known upfront. Prefer the `entry`
/// method when it's possible to use.
///
/// # Panics
///
/// `key` must be called before `value` and each call to `key` must be followed
/// by a corresponding call to `value`. Otherwise this method will panic.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<(String, i32)>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_map()
/// .key(&"whole").value(&self.0) // We add the "whole" entry.
/// .finish()
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
/// r#"{"whole": [("A", 10), ("B", 11)]}"#,
/// );
/// ```
#[stable(feature = "debug_map_key_value", since = "1.42.0")]
pub fn value(&mut self, value: &dyn fmt::Debug) -> &mut Self {
self.value_with(|f| value.fmt(f))
}
/// Adds the value part of a new entry to the map output.
///
/// This method is equivalent to [`DebugMap::value`], but formats the
/// value using a provided closure rather than by calling [`Debug::fmt`].
#[unstable(feature = "debug_closure_helpers", issue = "117729")]
pub fn value_with<F>(&mut self, value_fmt: F) -> &mut Self
where
F: FnOnce(&mut fmt::Formatter<'_>) -> fmt::Result,
{
self.result = self.result.and_then(|_| {
assert!(self.has_key, "attempted to format a map value before its key");
if self.is_pretty() {
let mut slot = None;
let mut writer = PadAdapter::wrap(self.fmt, &mut slot, &mut self.state);
value_fmt(&mut writer)?;
writer.write_str(",\n")?;
} else {
value_fmt(self.fmt)?;
}
self.has_key = false;
Ok(())
});
self.has_fields = true;
self
}
/// Adds the contents of an iterator of entries to the map output.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<(String, i32)>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_map()
/// // We map our vec so each entries' first field will become
/// // the "key".
/// .entries(self.0.iter().map(|&(ref k, ref v)| (k, v)))
/// .finish()
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
/// r#"{"A": 10, "B": 11}"#,
/// );
/// ```
#[stable(feature = "debug_builders", since = "1.2.0")]
pub fn entries<K, V, I>(&mut self, entries: I) -> &mut Self
where
K: fmt::Debug,
V: fmt::Debug,
I: IntoIterator<Item = (K, V)>,
{
for (k, v) in entries {
self.entry(&k, &v);
}
self
}
/// Marks the map as non-exhaustive, indicating to the reader that there are some other
/// entries that are not shown in the debug representation.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<(String, i32)>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// // Print at most two elements, abbreviate the rest
/// let mut f = fmt.debug_map();
/// let mut f = f.entries(self.0.iter().take(2).map(|&(ref k, ref v)| (k, v)));
/// if self.0.len() > 2 {
/// f.finish_non_exhaustive()
/// } else {
/// f.finish()
/// }
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![
/// ("A".to_string(), 10),
/// ("B".to_string(), 11),
/// ("C".to_string(), 12),
/// ])),
/// r#"{"A": 10, "B": 11, ..}"#,
/// );
/// ```
#[stable(feature = "debug_more_non_exhaustive", since = "1.83.0")]
pub fn finish_non_exhaustive(&mut self) -> fmt::Result {
self.result = self.result.and_then(|_| {
assert!(!self.has_key, "attempted to finish a map with a partial entry");
if self.has_fields {
if self.is_pretty() {
let mut slot = None;
let mut state = Default::default();
let mut writer = PadAdapter::wrap(self.fmt, &mut slot, &mut state);
writer.write_str("..\n")?;
self.fmt.write_str("}")
} else {
self.fmt.write_str(", ..}")
}
} else {
self.fmt.write_str("..}")
}
});
self.result
}
/// Finishes output and returns any error encountered.
///
/// # Panics
///
/// `key` must be called before `value` and each call to `key` must be followed
/// by a corresponding call to `value`. Otherwise this method will panic.
///
/// # Examples
///
/// ```
/// use std::fmt;
///
/// struct Foo(Vec<(String, i32)>);
///
/// impl fmt::Debug for Foo {
/// fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
/// fmt.debug_map()
/// .entries(self.0.iter().map(|&(ref k, ref v)| (k, v)))
/// .finish() // Ends the map formatting.
/// }
/// }
///
/// assert_eq!(
/// format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
/// r#"{"A": 10, "B": 11}"#,
/// );
/// ```
#[stable(feature = "debug_builders", since = "1.2.0")]
pub fn finish(&mut self) -> fmt::Result {
self.result = self.result.and_then(|_| {
assert!(!self.has_key, "attempted to finish a map with a partial entry");
self.fmt.write_str("}")
});
self.result
}
fn is_pretty(&self) -> bool {
self.fmt.alternate()
}
}
/// Creates a type whose [`fmt::Debug`] and [`fmt::Display`] impls are provided with the function
/// `f`.
///
/// # Examples
///
/// ```
/// #![feature(debug_closure_helpers)]
/// use std::fmt;
///
/// let value = 'a';
/// assert_eq!(format!("{}", value), "a");
/// assert_eq!(format!("{:?}", value), "'a'");
///
/// let wrapped = fmt::from_fn(|f| write!(f, "{value:?}"));
/// assert_eq!(format!("{}", wrapped), "'a'");
/// assert_eq!(format!("{:?}", wrapped), "'a'");
/// ```
#[unstable(feature = "debug_closure_helpers", issue = "117729")]
pub fn from_fn<F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result>(f: F) -> FromFn<F> {
FromFn(f)
}
/// Implements [`fmt::Debug`] and [`fmt::Display`] using a function.
///
/// Created with [`from_fn`].
#[unstable(feature = "debug_closure_helpers", issue = "117729")]
pub struct FromFn<F>(F)
where
F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result;
#[unstable(feature = "debug_closure_helpers", issue = "117729")]
impl<F> fmt::Debug for FromFn<F>
where
F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
(self.0)(f)
}
}
#[unstable(feature = "debug_closure_helpers", issue = "117729")]
impl<F> fmt::Display for FromFn<F>
where
F: Fn(&mut fmt::Formatter<'_>) -> fmt::Result,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
(self.0)(f)
}
}